KR880000521B1 - Axial-flow fan - Google Patents

Abstract

An axial flow fan for reducing noise caused by air-flow has parameters satifying following conditions that BR=0.07-0.2 DT, DB=1.01-1.04 DT, ld=0.04-0.1 DT, lx=0-0.04 DT where BR; half radius of curved edge of the outer frame, DT; outer radius of the fan, DB; inner radius of the bell mouth, ld; duct distance of the bell mouth, lx; distance between back part of the outer wing of the fan and the end part of the duct.

Description

Axial flow fan

1 is a front view of a conventional axial blade.

2 is an exploded perspective view of an axial fan according to an embodiment of the present invention.

3 is a front surface diagram showing the definition of δθ in the above-described embodiment.

4 is a rotational projection about a plane including a rotation axis showing the definition of δ z.

5 is a cross-sectional view showing the tip of the wing.

Figure 6 is a front view showing the mutual position of the wings.

7 is a sectional view showing the relative relationship of flow to the wing.

8 is a characteristic diagram based on experimental results showing the values of non-noise level and open-point noise level for the change of δz.

9 is a characteristic diagram based on experimental results showing the values of non-noise level and open-point noise level for the change of δθ.

10 is a characteristic diagram based on experimental results showing the values of the noise level and the open point noise level for the change of θt.

11 is a characteristic diagram based on experimental results showing the values of the non-noise level ks and the open point noise level for the change of ξt.

12 is a side view showing the relationship between the wing and the bell mouth (bell mouth).

13 is a characteristic diagram showing the relationship between the magnitude of R and the minimum non-noise level of the bell mouse.

Fig. 14 is a characteristic diagram showing the relationship between the length ld of the bell mouth of the bell mouse and the minimum noise level.

* Explanation of symbols for main parts of the drawings

1: Wing 1 ': Wing in front projection

1a: Wing tip 1a: Wing tip in front projection

1b: Front part of a wing 1b: Front edge of a wing in front projection degree

1c: Wing trailing edge 1c ': Wing trailing edge in front projection

1d: Outer wing housewife 1d ': Outer wing house in front projection

2: boss 3: rotation axis

4: direction of rotation 5: camber line

5a: wing pressure surface 5b: wing pressure surface

5c: relative camber line 6: parallel axis of rotation axis

7: wing surface inflow vector 8: pressure side peeling area

9: centrifugal force due to flow between wings

9a: Normal component of the wing pressure surface of centrifugal force

9b: Parallel component of wing pressure side of centrifugal force

10: Bellemouth

10a: Suction plane of Bellemouth 10b: R part of Bellemouth

10c: Duct of Bellemouth Rt: Radius of outer circumference of wing

Re: Blade tip position radius Rb: Boss radius

R: Radius PR: Center of Ikhyeon Line

PR ': Iksi Centerline in Front Projection

Pt: wing line centerline of wing outer periphery

Pt ': Ikji center point of the outer periphery of the wing in the total projection

Pb: Ikseon center point of boss outsourcing

Pb ': Iksi Center of Boss Outsourcing

0: origin of boss in front projection X: X axis

δθ: angle with respect to the X axis of the center of the ship line in radius R

Sc: Plane perpendicular to the axis of rotation past Pb

Ls is the distance between the leading line center point of radius R and the Sc plane

δz: Angle formed by Sc plane and line segment Pb.PR

L: Length of blade string DT: Outer diameter of van

θ: camber angle DB: inner diameter of bell mouse

ξ: wing stagger angle BR: size of R part of bell mouse

PR: Reference radius of arc wing

ld is the length of the duct of the bell mouse

t: Pitch

lx: Distance between wing outer peripheral edge and duct end

The present invention relates to an axial flow fan used in the ventilation fan, the air conditioner, and the like of the present invention, and more particularly, to provide an axial flow fan capable of lowering the aerodynamic noise.

Axial fans are widely used in air conditioners, ventilation fans, etc., and it is very socially important to reduce the noise generated by the fans as much as possible. However, the design method of the low noise fan that lowers the noise generated by the fan as much as possible and does not lower the aerodynamic performance of the fan has not been established, and the trial and error design method applied to the individual products is applied. come.

Among these prior arts, many methods have been used, such as making the front shape of the impeller projected in the direction of rotation visible in Japanese Patent Application No. 50-39241.

1 shows the front shape of the impeller according to the patent, 1 is the impeller wing, 2 is the boss attaching the wing 1, 1a is the tip of the wing 1, Rt is the outer radius of the impeller, and Re is the wing This is the radius of the tip 1a.

Conventionally, in this type of impeller, there is no clear judgment technique regarding the method of determining the position of the outer periphery and the method of determining the leading edge, and a method such as simply defining the shape only by the uniqueness of the front shape has been applied.

In FIG. 1, the wing tip portion 1a is located at a radius ratio Re / Rt = 0.88, and there is no place at Re / Rt ≒ 1.0 near the outer circumference of the impeller, thereby substantially reducing the area of the wing outer circumference having the largest amount. As a result, noise is increased by causing a decrease in aerodynamic performance.

The wing tip of the side flow fan is very important from the aerodynamic point of view. The fact that the shape has a large shape in the direction of the rotational axis is a great resistance to the fluid and the induction of the leading edge peeling at the leading edge of the wing. In addition, the noise generated from the wing surface is increased.

In addition, in the conventional impeller, the flow of the wing is considered to be a simple two-dimensional flow, and the shape is determined. Therefore, the noise characteristics at the opening point can be improved, but the noise characteristics at the time of static pressure generation, which is the actual fan use mode, can be determined. There is no big improvement.

Therefore, the three-dimensional handling of the wing type is not abundant in the fan of Japanese JP 50-39241, so even if the fan configuration is used, the noise characteristics can be dramatically improved and an ultra-low noise side flow fan can be constructed. none.

The present invention and other inventions of the present invention have been made to improve the shortcomings of the conventional side flow fans, and an object of the present invention is to provide an ultra low noise axial flow impeller, which has not existed so far by clarifying the three-dimensional shape of the impeller.

An embodiment of the present invention will be described with reference to the drawings.

2 is a perspective view of the axial flow fan according to the present embodiment in the shape of three wings, and the bell mouse portion is disassembled and displayed. 1 is a three-dimensional wing, 1 ^a is the wing tip, 1 ^b is the wing leading edge, 1 ^c is the wing trailing edge, 1 ^d is the wing outer periphery, 2 is the boss to attach the wing (1), and 3 is the The axis of rotation 4 is the direction of rotation.

This wing, as you know in the drawing, is unique in the shape of a wing and has not existed until now.

Specifically, the factors constituting the outlet fan according to the present invention are shown.

The impeller is designed to specifically define the three-dimensional shape of the wing by clarifying the various factors constituting the fan, and is the optimal shape obtained from the vast test results.

As an important parameter for determining the three-dimensional shape of the axial fan, the present invention defines the position of the blade center line P _R of the blade.

3 is a projection view when the wing 1 is projected on a plane orthogonal to the rotation axis 3, 1 'is a wing shape on the projection surface of the wing 1, 2 is a boss, 3 is a rotation axis, and a rotation axis 3 The circular arc 1 _b R'-P _R '-1 _CR ' in the projection plane when the blade 1 is cut from the cylindrical surface of radius R in the shape of a wing cross section.

P where _R 'is a circular arc 1 _bR' and the center line of -1 _CR ', is a chord center line of the projection plane.

In order to clarify the position of P _R 'on the projection surface, the projection plane of the rotation axis 3 is assumed to be Pb', with the boss subforeign line center point on the projection surface when the blade 1 is cut off from the cylindrical surface of the boss radius Rb. A coordinate system in which the straight line Pb'-0 connecting 0 in the X axis and the zero origin is formed on the projection plane.

P _R ′ represents the angle between the tangent and the radius (R) of the ship center point locus (Pb'-P _R '-Pt') at the ship center point (P _R ').

In addition, the code | symbol with a dash (') symbol represents each part in a projection surface.

"When the angle is ₀ and the _R-X axis to achieve δθ, and a distance R, P 'line P in the coordinate position of the _R can be expressed in polar coordinates, called (R, δe).

In the present invention, when the angle formed by the straight line pt'-0 and the x-axis is δθ't, δe = δθtx

(Rt: blade tip radius, Rb: boss radius) and δθt = 40 ° -50 °.

Thus, since the position of the shipwreck center point R _R can be defined on the plane orthogonal to the rotation axis 3, it is defined as an axial position next.

FIG. 4 shows the airfoil center point P at an arbitrary radius R with respect to the radial trajectory Pb'-P _R '-Pt' from the boss side wing core center point Pb 'in FIG. 3 to the outer peripheral ship center line point Pt'. _R in the plane (OX) side, and displays the section in the same position in the radial distribution of the chord center line of rotation in the projection radius (R) P _R and the wing (1). In the figure, 9 is the centrifugal force at the time of rotation of the impeller, 9a, 9b are the angular pressure surface normal component and tangential component of the centrifugal force 9, and arrow A indicates the inflow direction of the gas.

Here, a planar Sc plane orthogonal to the rotation axis 3 is considered, passing through the center line Pb of the blade line 1 at the outer circumferential portion of the boss 2.

이 된다.When the center of the ship line at an arbitrary radius R is P _R , the distance between the Sc plane and the front of P _R is Ls, and the angle between the boss sub-ship line center point (Pb) and the Sc plane is δz, where δz = tan− One

Becomes

Therefore, by defining Ls or δz to give a radius R, the axial position of the blade center point P _R can be defined.

In order to construct an impeller, the blade line center point P _R may be a relative origin, and a wing section given by a camber may be formed thereon, and the entire wing surface may be a smooth curved surface. FIG. 5 shows a developed view when the blade 1 is cut from the cylindrical surface of radius R when the wing surface is formed with the center line P _R as the relative origin, and the cross section is developed in a two-dimensional plane. Since the camber wire 5 of the blade uses a circular arc in this embodiment, in order to form the circular arc, the center angle θ, the radius for forming the arc (P _R ), the leading edge of the blade (1 _b ), and the trailing edge (1 _c ).

+θb로 하고 이때 θt는 날개끝에서 캠버 각, 즉 날개끝에서의 캠버선의 중심각, θb는 날개보스부에서의 캠버각, 즉 날개부스부에서는 켐버선의 중심각을 부여하고 θt=20°-30°, θt=27°-37°, θt<θb로 한다.In this embodiment, the radial distribution of θ is θ = (θt−θb) ×

where θt is the camber angle at the tip of the wing, ie the center angle of the camber line at the tip of the wing, θb is the camber angle at the wing boss, ie the center angle of the camber line at the wing booth, and θt = 20 ° -30 ° ,? t = 27 ° -37 ° and? t <θb.

와 회전축(3)과 평행한 직선(6)간의 각도를 엇갈림 ξ로 하고, ξ를 반경방향으로 분포되도록 결정한다.Wing position is winged

And the angle between the rotation axis 3 and the straight line 6 in parallel to the staggered ξ, it is determined that ξ to be distributed in the radial direction.

+ξb로 하며 이때 ξt는 날개끝에서의 엇갈림각, ξb는 날개 보스부에서의 엇갈림각으로 하고 ξt=62°-72°, ξb=53°-63°, ξt>ξb로 하고 있다.That is, the radial distribution of ξ is ξ = (ξt + ξb) ×

where ξt is the staggered angle at the tip of the wing, ξb is the staggered angle at the wing boss, and ξt = 62 ° -72 °, ξb = 53 ° -63 °, and ξt> ξb.

L is the length of the chord, and is a parameter called T / L using the circumferential distance T between the wings shown in the sixth, and defines the size of the radial wing.

As described above, the ultra-low noise axial impeller is obtained by setting the five parameters as independent values.

If the fan is to be quiet, the simplest method is to lower the speed of the fan to lower the airflow. However, this method reduces the sound, but greatly reduces the basic function of the fan.

In other words, the air volume decreases, so that a static pressure increase cannot be obtained. Here, the flow pattern of the impeller (radial distribution of the rotational velocity component of the airflow) is defined as a free vortex (Cu × R = constant, Cu: rotational velocity component of the airflow, R: radial angular momentum of the radial airflow). Work regularly from the boss part of this constant wing to the outer circumference part.

In this case, the forced vortices (Cu = R × constant, Cu: airflow vortices), which cause a large work at the outer periphery of the wing with a large circumferential speed at the inlet to the outlet in the radial distribution of the streamline. The directional velocity component, R: radius, and the angular momentum of the air flow increase in proportion to the radius) are used to reduce noise by lowering the fan speed without lowering the air volume and static pressure. However, the air flowing into the wing surface has a vortex-free periodic flow unless its external force is applied.

Therefore, even though impeller vane flow is forced vortex, the impeller designed as forced vortex because the flow before flowing into the wing flows into free vortex (axial flow velocity is constant at each radial position of the impeller). Close to the boss of the impeller, as shown in FIG. 7, the relative inflow angle ε becomes large.

Since the collision-free inflow angle to the wing 1 is γ, the tendency of ε> γ is strong, so that the flow 7 entering the impeller causes global peeling on the pressure surface 5b of the wing and the separation zone 8 increases. This increases the continuous frequency noise generated by the blades.

This tendency is prominent near the open point with a lot of airflow. That is, as the amount of air increases, the relative inflow angle ε gradually increases and the peeling region 8 increases.

Therefore, if the stagger angle ξ of the wing is reduced to lower the noise near the opening point, when the positive pressure is generated, the attack angle α becomes excessively large and peeling occurs at the negative pressure surface 5a, causing the wing to stall. do.

Here, it is necessary to optimize the shape of the leading edge of the wing to lower the noise near the opening point and lower the noise when the static pressure occurs.

In the present invention, in order to obtain the above characteristics, the three-dimensional distribution of the center line of the shipboard is defined, and the overall shape of the impeller is determined.

Here, the value of the parameter which determines the basic wing shape in this invention is shown next.

δz = 22.5 ° (radius constant)

δθ = 45 ° ×

+32°θ = -7.5 ° ×

+ 32 °

T / L = 1.05 (radius constant)

(Rt: Wing Tip Radius, Rb: Wing Boss Radius)

In the basic blade, the radial distribution of δθ is linear with respect to the radius R, so the tangent and radius of the center line trajectory Pb'-P _R '-Pt: in the center of the shipwreck center P _R ' in FIG. The angle Pθ 'formed by R rapidly increases as the head portion of the boss faces the tip of the blade.

In addition, by forming the center line of the shipboard line so that P _R is delta z = 22.5 °, the actual camber line formation of the blade with respect to the flow at the blade leading edge is in a state where the camber angle θ is reduced as in 5c.

In other words, in the flow flowing into the blade leading edge, the streamline shape on the wing actually has a centrifugal force acting on the fluid due to the rotation of the blade. Since it flows in the form as shown in (7), the blade leading edge and the position of the streamline at the point where the wing surface is slightly entered are not changed excessively in the axial direction.

In such a streamlined form, it is possible to achieve a state in which the flow 7 flowing into the wing flows into a collision-free state, that is, ε ≒ r, and the peeling zone 8 at the pressure side disappears and noise is generated. Becomes very small.

The combination of δz and δθ is best for the basic type, but in designing the fan, this value may need to be changed due to the limitation of the axial dimension.

Therefore, experimentally, each meter was set to the most optimal value, and the result of experimenting with a few wings with different values showed that the results are shown in FIG. 8 and FIG.

As shown in FIG. 8, when the value of δz is between 12.5 ° and 32.5 °, the minimum non-noise level Ks is sufficiently low and is very low noise. The non-noise level Ks (phone) is defined as follows.

Ks = SPL-10 × log (Q Ps2.5)

SPL: Noise Level (Phone) Q = Flow (㎥ / min)

Ps = static pressure (mmAq)

In addition, when the δz increases, the noise level decreases as the δz increases, but the degradation degree is saturated at δz = 32.5 ° or more, and the maximum value of δz is 32.5 ° in terms of strength.

9 shows the change in the noise level at the open point of change in the non-noise level due to the value of δθ.

As is also known in the drawing, if the condition of??

Practically, the larger the δθ is, the lower the noise tends to be, but the maximum is about 50 ° from the point of bending strength. Therefore, if a value exists between δθ = 40 ° to 50 °, the noise can be sufficiently lowered.

In addition, in order to optimize the leading edge shape as above, it is distributed radially in δθ and δz, so that the wing surface is inclined to the suction shaft as a whole, so that it passes through the wing surface while drawing the trajectory of the arc. The centrifugal force acts largely on the wing negative pressure surface by the flow of the blades.

That is, in Fig. 4, the negative pressure side side normal component 9a of the centrifugal force 9 becomes a large compressive force with respect to the speed boundary layer developed on the negative pressure surface 5a, and the boundary layer can be made very thin.

Since aerodynamic noise generated on the negative pressure surface 5a side is linearly proportional to the thickness of the boundary layer, the fact that the boundary layer can be made thinner reduces noise generated.

In addition, since an extrusion force, such as the negative pressure side side normal component 9a, acts on the boundary layer, a strong inhibitory action is generated against the separation of the boundary layer on the negative pressure surface 5a due to an increase in the angle of attack of the wing in the low wind volume region, thereby causing the blade to stall. 않게) not to get a wider operating range can be obtained.

Next, the distributions of the gamber angle θ and the stagger angle ξ, which are one of the functional elements of the wing, are solved.

The camber angle θ is an important amount for determining the amount of work performed by the wing element in the case of an arc-shaped impeller.

In general, the larger the θ, the more the blades work at the same rotation. However, the larger the θ, the higher the noise. So all the other parameters were of the basic type, and noise was measured for several wings with different distributions of θ.

+θbThat is, θ = (θ t -θ b) ×

+ θb

In the distribution equation, it is understood that when the experiment is conducted at θb = 32 °, the non-noise level is sufficiently small at θt = 20 ° to 30 °, resulting in a very low noise blade.

Although not shown in the drawing, this trend does not change even if the value of θb is changed to 27 ° to 37 °.

As described above regarding the distribution of blade stagger angle ξ, δθ and δz are optimized, and the flow pattern at the blade leading edge is close to free vortex, so that the blade stagger angle ξ is also strong with respect to the relative inflow angle ε. affect. Here, how to distribute the wing angle ξ

+ξbξ (ξt-ξb) ×

+ ξb

By measuring the noise of several wings with all other parameters as the basic shape, the same result can be obtained in FIG.

It is clear from the drawing that ξt = 62 ° -72 ° and ξb = ξt-9 °, that is, ξb = 53 ° -63 °, can obtain a fan of actor low noise.

In the present invention, the pitch suspension ratio T / L = 1.05. In other words, the longer the length L of the blade with respect to the same work, the smaller the camber angle θ.

However, T / L = 1.0 is the limit when forming a wing with a press or the like on a single plate, and even in the case of plastic molding, this value is a limit in relation to mold. On the other hand, increasing T / L causes noise to increase as described above.

Therefore, the maximum value of T / L is a limit value of T / L = 1.2 in which noise is increased by about two phones.

In terms of the radial distribution of T / L, it is better to make it almost constant in the radial direction in order to make the edge of the blade surface as special shape as above. In particular, an excessively large T / L at the outer periphery causes an increase in noise. do.

In terms of strength, the axial flow impeller according to the present invention basically has a structure in which the center line of the blade line is arranged on the surface of the cone, and the method of distributing the camber angle θ is 24.5 ° at the outer circumference and 32 ° at the boss. Has a curved shape curved in the radial direction, and the flexural strength is much higher than that of a conventional planar blade.

For this reason, the blade may be formed by a plate of about 2 mm in the case of the blade, which has conventionally had to use a plate of 3 mm or more in thickness, so that the material cost can be greatly reduced.

In addition, since the blade thickness can be made thinner, the weight of the fan can be reduced, and thus the load on the motor can be reduced, so that the motor can be driven by a less full power motor and energy can be saved.

In addition, since the boundary layer of the wing pressure surface can be strongly compressed, the secondary flow generated on the wing surface is also suppressed, thereby increasing the efficiency.

In addition, in the present embodiment, the number of the number of wings is about three, but if the essential parameters are set as described above, the same effect is obtained regardless of the collection of the wings.

In addition, the combination with the bell mouse is important when using the wing as a fan of lower noise.

So, systematically, a combination test with Bellemouth was used to construct a shape with a very low minimum noise level. In order to reduce the minimum noise level, the bell mouse shape must be stalled as long as it can become a fan.

12 is a view showing the relative position of the bell mouse and the impeller used in the present invention, 10 is the bell mouse body, 10a is the R portion of the bell mouse 10 orthogonal to the axis of rotation (3), 10 c is the bell mouse (10) ), Duct part 7 is air flow.

Here, the basic shape of the type lowering the minimum noise level is indicated.

BR = 0.117DT

ld = 0.0667DT

DB = 1.017DT

lx = 0

Where DT is the diameter of the impeller, BR is the size of the R portion of the bell mouse 10, ld is the duct length of the bell mouse 10, DB is the inner diameter of the bell mouse 10, lx is the duct of the bell mouse 10 It is the distance between the five edges of the hem and the wing 1.

The axial blade (1) has a large amount of protrusion to the suction side, and the larger work on the outer peripheral portion of the wing (1), and furthermore, because the free edge in the leading edge (1b) features a bell mouse shape to make use of this feature.

Since the bell mouse 10 according to the present invention has a suction plane 10a, the suction flow flows into the wing 1 as an air stream 7 along this plane 10a.

Since the conventional bell mouse has no suction plane 10a, flow is separated at the tip of the bell mouse and turbulence enters the impeller. In the case of the bell mouse of the present invention, since there is no peeling at the tip, noise generation due to abnormal lifting force of the wing due to the suction turbulence is generally very small.

Since the outer circumferential edge of the wing 1 is covered with the duct 10c, the leakage at the outer circumference of the wing 1 is reduced and works effectively up to the trailing edge of the outer circumference, thereby obtaining a large static pressure rise. The noise level is greatly reduced.

Since the basic bell mouse shape may have to be changed due to dimensional constraints during assembly, the characteristics test was performed by changing the size BR and the duct length ld of R of the bell mouse 10b. All other shapes were taken as basic shapes.

FIG. 13 shows the experimental results of the minimum specific noise level for the R portion BR of the bell mouse 10. It can be seen that if BR = 0.07DT to 0.2DT, a sufficiently low axial flow fan can be obtained.

FIG. 14 shows the relationship between the duct length ld and the minimum non-noise level of the bell mouse 10. It can be seen that a low noise fan can be obtained if ld = 0.04DT to 0.1DT.

In particular, with respect to the duct length ld, if ld is too large, it tends to inhibit the flow of the airflow 7 from the outer periphery of the wing 1 and to increase the noise.

Regarding the inner diameter DB of the bell mouse 10, the closer to the impeller outer diameter DT, the more difficult it is to surgise. However, DB = 0.01DT is a limitation in terms of manufacturing. However, if the DB is large, it is easy to suddenly surge, so that DB = 1.04DT, in which the increase in the minimum ratio noise level is about 3 phons, becomes the limit of the larger one.

The distance 1x between the end of the duct 10c and the trailing edge of the outer periphery of the blade 1 should be basically lx = 0. Note that even if the distance lx by DT does not change performance, it becomes a low noise fan.

According to the present invention described above, the use of axial blades optimized for δz and δθ, which are essential parameters of the blades, and the optimization of the bell mouse shape, thus providing an axial fan having a very low minimum noise level with large air volume and fixed pressure. There is.

In addition, according to the present invention, the above-described effects are more enhanced because the axial blades having optimized parameters θ and ξ are used.

Claims (2)

The axis of rotation passes through the center of the ship line P _R at the cross section when cutting the impeller from the cylindrical surface of the radius R around the axis of rotation, and the center of the ship line Pb at the cross section when the boss portion of the blade is cut at the cylindrical surface of the radius Rb. When the distance between the plane Sc and the plane Sc is orthogonal to Ls, in the coordinate system in which the intake side of the air flow is in the forward direction, the point P _R is always located in the forward direction with respect to the plane Sc so that δz = tan ₋₁

The value of δz expressed by δz is set to δz = 12.5 ° to 32.5 °, and in the projection plane at the time of projecting the wing surface to a plane orthogonal to the axis of rotation, the boss portion of the blade in the cross section at the time of cutting from the cylindrical surface of radius Rb In the coordinate system in which the straight line connecting the zero point and the Pb 'point is the X axis with the rotation axis set as the origin zero and the axis of rotation is set to zero, the PRX center point when the blade plane is cut from the cylindrical surface of radius R is PR'. When the angle between the straight line PR'-0 and the X axis is δθ, the radial distribution of δθ is obtained. δθ = δθt ×

(Rt: wing tip radius, Rb: wing boss radius, δθt: angle between the straight line pt'-0 and the X axis), and give δθt = 40 ° ~ 50 °, and there is a plane orthogonal to the rotation axis and radius from there BR is narrowed to a curved surface and has a straight portion ld and has an inner diameter DB with respect to the wing outer diameter DT. When the fan position is lx as the distance between the trailing edge and the end of the duct at the outer circumference of the wing, Value of size BR = 0.07DT ~ 0.2DT DB = 1.01DT ~ 0.04DT ld = 1.04 ~ 0.1DT lx = 0 ~ 0.04DT Axial flow fan, characterized in that as. Plane orthogonal to the axis of rotation passing through the center line PR of the tip line in the cross section at the time of cutting the impeller on the cylindrical surface of radius R with the central axis of rotation as the center, and the center point Pb at the cross section at the cutting edge of the cylindrical section of radius Rb. When the distance between Sc is Ls, in the coordinate system in which the intake side of the air flow is in the forward direction, the point P _R is always located in the forward direction with respect to the plane Sc so that δz = tan _-1

The value of δz expressed by δz is set to δz = 12.5 ° to 32.5 °, and the blade edge of the blade is cut at the cylindrical surface of the radius Rb in the projection surface at the projection surface when the blade surface is projected on a plane perpendicular to the rotation axis. In the coordinate system of the line center point Pb ', the rotation axis being the origin zero, and the straight line connecting the 0 point and the Pb' point as the X axis, the center line of the blade line when cutting the wing surface from the cylindrical surface of radius R is PR '. When the angle between the straight line PR'-0 and the X-axis is δθ, the radial distribution of δθ is obtained. δθ = δθt ×

(Rt: wing tip radius, Rb: wing boss radius, δθt: angle formed by the straight line Pt'-0 and the X-axis) to make δθ = 40 ° to 50 °, and cut the wing surface at the cylindrical surface of radius R. In a developed view in which the cross section is developed in a two-dimensional plane, a radial distribution of θ is obtained when the shape of the camber line on the wing section is made into an arc shape and the center angle for forming the arc is θ. θ (θt-θb) ×

+ θb (θt: camber angle at the tip of the blade, θb: camber angle at the wing boss), and θt = 20 ° to 30 °, θb = 27 ° to 37 ° and θt <θb. Ξ = (ξt-ξb) × where ξ is the angle formed by the straight line passing through the leading edge of the blade parallel to the axis of rotation and the axis of rotation of ξ.

+ ξb (ξt: staggered angle at the tip of the wing, ξb: staggered angle at the wing boss), ξt = 62 ° ~ 72 °, ξb = 53 ° ~ 63 °, ξt> ξb, and the plane perpendicular to the axis of rotation In the suction bell mouse having a straight portion ld and having a straight portion ld and having an inner diameter DB with respect to the wing outer diameter DT, the fan position is the distance between the trailing edge portion and the duct length at the outer circumference of the blade. When we set the value of each parameter BR-0.07DT ~ 0.2DT ld = 0.04 to 0.1DT DB = 1.01 DT-1.04DT lx = 0 to 0.04DT Axial flow fan, characterized in that as.

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